in praise of RawTherapee, "Amaze" demosaicing algorithm

Started Jun 10, 2011 | Discussions thread
RussellInCincinnati
Senior MemberPosts: 3,186
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Raw Therapee great. Amaze no better at "normal" print sizes
In reply to RussellInCincinnati, Jun 26, 2011

GaryW and Ck3 have raised the question of the significance of Amaze demosaicing at normal print sizes (rather than huge, 100% magnification pixel-peeping of 3 foot high images on our monitors). Thus have prepared below (what's amazing is how long these comparisons take to prepare) 5 images, taken on a tripod, with remote release, from a pretty perfect multicoated enlarging lens, being used at its designed-for optimum distance, at F9.5:

  1. Typical AHD demosaicing in RT Raw Therapee, no unsharp mask sharpening as is quite typical, at huge magnification. Nex does nicely.

  2. Amaze demosaicing in RT, RL Deconvolution mild sharpening but also no unsharp mask, at huge 1 meter high print size. Noticeably crisper than AHD demosaicing, and at the same time a touch less noise. Seems like a win for Amaze+RLD, and the Nex looks to be larger sensor DSLRs a run for their money.

  3. Picture number 1, but the AHD-demosaiced image has now been put through typical radius 1 unsharp mask sharpening. Now the AHD image looks as sharp as the Amaze image number 2. But, the noise is of course still tiny a bit worse than in the Amaze image. Not to say the noise is real bad in any of the images.

  4. Typical AHD demosaicing plus unsharp mask, at a reasonable print size. Raw conversion took just a few seconds.

  5. Amaze demosaicing plus RL Deconvolution plus unsharp mask. Raw converstion took at least 1 minute. Appears identical in every way to AHD demosaicing, at this normal print size. Darn, didn't think of taking a JPEG at the same time, but this was a real assignment not a test session.

My original post praised Raw Therapee plus the Amaze demosaicing algorithm. My opinion after this test is that Raw Therapee, with all its defaults, does an almost perfect job of "developing" raw files. For example the above AHD images are all straight out of Raw Therapee with everything defaulted, and the color and brightness are almost perfectly natural (well the darkest tones need a bit of pulling down). Of course someone might want to add more color saturation or contrast to their images, but it's nice to start with natural accuracy, and it's much easier to contrast and saturation than it is to take them away when you've overshot.

But can now see that Amaze demosaicing and RL Deconvolution are only advantageous at huge magnifications. At normal print sizes from not-very-much-cropped Nex raw files, typical AHD demosaicing results are indistinguishable from the output of the new Amaze demosaicer.

Unless there is a moire false color problem, which (shown in this thread) Amaze does a bit better with at any print size. But then most images do not have moire problems.

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